I have tried Spanish Jasmine, It seems to naturally root easily in just plain water.

Most of the passiflora/passionfruit vines I have tried seem to root okay in water. The blue skyvine roots easily in water. I am trying corkscrew vine now, it has been 2 wks and no sign of rooting on those but sometimes it takes awhile. I think on the plant propagation forum someone made a list of what is easy to root in plain water. You might try doing a search.

I found the link it pertains more to perennials but it is a good informative thread. I think clematis, ivy, pothos, the fuzzy purple passion vine (gynura sp?) are all mentioned.

Here is a link that might be useful: what will root in water

As SJN mentioned many passifloras root well in water especially with bottom heat. Mexican Flame vine roots very easily, Clerodendron speciosa, Clerodendron thomsonaie & Malabar spinach are some others that will water root.
Karyn